Severe forms of sleep apnea (SA) are known to be associated with increased morbidity and mortality. Limited evidence suggests that the milder, yet highly prevalent forms of the disorder may also be associated with increased risks of cardiovascular disease and hypertension. The present proposal is an application for one of the field centers in response to RFA-NIH-HL-94-09-L. Our main objective is to assess whether SA is independently related to prevalent and incident coronary heart disease, stroke, hypertension and subclinical atherosclerosis. In collaboration with the other centers, we also plan to examine whether the postulated SA- related risk of clinical cardiovascular disease is modified by subclinical atherosclerotic disease, hypertension, age, gender and race. Additional objectives include investigating the short-term natural history of the disorder, the level of SA awareness in participants, the impact of SA on quality of life, and compliance with diagnostic and treatment recommendations in those identified with SA. We will also estimate costs associated with both SA-related cardiovascular morbidity, and those related to diagnosis and treatment of SA in the population. We propose recruiting 1,100 participants of both sexes, ages 53 or older, selected from the Washington County cohorts of the ongoing NHLBI-sponsored prospective Atherosclerosis Risk in Communities (ARIC) Study and Cardiovascular Health Study (CHS). Participants will be mostly white, reflecting the racial composition of County. Information on risk factors has been collected repeatedly since the inception of these studies (1987- 89). Available for both cohorts are B-mode ultrasound data on intima+media thickness of the carotid arteries, an expression of subclinical atherosclerosis, echocardiography for CHS participants, currently aged 73 years or older, and retinal photography for ARIC participants, currently aged 53-72 years. Both parent studies meet the RFA's requirement that data should have been collected within five years of the initiation of the sleep studies. Ascertainment of outcomes is highly standardized, and follow-up rates are very high. For the selection of the study population, participants will be stratified according to their snoring history. A home sleep study will be conducted on all participants, followed by full polysomnography (PSG) in those with abnormal results and in a random sample of individuals found to be normal in the home study. The latter sample will be used to validate the results of the home study. The sleep examinations will be completed in two years. We will then assess the associations of SA and related disorders with cardiovascular disease prevalence, incidence and risk factors, ascertained through clinic examinations and procedures used in ARIC and CHS. A second PSG will be conducted in selected participants for comparing SA cases and controls, in order to address the other objectives of the study, including the evaluation of the impact of sleep related disorders on quality of life, and the short term natural history of SA.